Devices are designed to operate in a wide variety of environmental conditions. These conditions can include temperature ranges, UV exposure, humidity, pressure, and the like. The conditions upon which the device is designed are referred to as expected operating conditions or mission profiles.
The design process considers the mission profiles when selecting materials, components, fabrication procedures, and the like. Then, qualification testing is done on prototype devices to determine if the designed devices meet the mission profiles.
Once in use, the devices encounter conditions that may or may not be conditions expected from the mission profile. Devices may have faults or fail prematurely due to manufacturing errors, design errors, unexpected operating conditions, misuse, and the like. It may be difficult to determine the cause of the premature failure. Additionally, if the cause of the failure is not known, corrective action cannot be taken.